Example of Successfully Adding Facets to a Face Group?

I'm trying to use addSelectedFacetsToFaceGroup() but I always get "Result of expression is not a function."

Using addSelectedFacetsToMaterialGroup() works fine in the exact same spot and I get expected results.

The documentation is non-existant on both of these.  Just one page that mentions they were added in 4.11.

Any examples of this being used correctly?

Thanks